Because, dear Blazing Tempest, the good team at Pokémon decided to screw me over by only allowing us to be Axew, Oshawott, Tepig, Snivy, and Pikachu. Also there's a pretty limited number of Pokémon in the game which just sucks. :/ So It's most likely that Totodile and Riolu don't even exist in the game.